Polymers for preventing or reducing aluminosilicate scale in a bayer process

ABSTRACT

Materials and a process are provided whereby polymers with the pendant group or end group containing —Si(OR″) 3  (where R″ is H, an alkyl group, Na, K, or NH 4 ) are used to control aluminosilicate scaling in a Bayer process. When materials of the present invention are added to the Bayer liquor before the heat exchangers, they reduce and even completely prevent formation of aluminosilicate scale on heat exchanger walls. The present materials are effective at treatment concentrations that make them economically practical.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 10/780,302, entitled “Polymers for Preventing orReducing Aluminosilicate Scale in a Bayer Process,” filed on Feb. 17,2004, which is a divisional of U.S. patent application Ser. No.10/201,209, entitled “Methods of Preventing or Reducing AluminosilicateScale in a Bayer Process,” filed on Jul. 22, 2002, which are bothincorporated in there entirety herewith.

BACKGROUND OF THE INVENTION

The Bayer process is almost universally used to manufacture alumina. Inthis process raw bauxite ore is first heated with caustic soda solutionat temperatures in the range of 140 to 250° C. This results in thedissolution (digestion) of most of the aluminum-bearing minerals,especially the alumina trihydrate gibbsite and alumina monohydrateboehmite, to give a supersaturated solution of sodium aluminate(pregnant liquor). Resulting concentrations of dissolved materials arevery high, with sodium hydroxide concentrations being greater than 150grams/liter and dissolved alumina being greater than 120 g/l. Anyundissolved solids are then physically separated from the aluminatesolution, and a polymeric flocculant is used to speed the removal of thefine solid particles. Residual suspended solids are removed by afiltration step. The filtered clear solution or liquor is cooled andseeded with alumina trihydrate to precipitate a portion of the dissolvedalumina. After alumina precipitation, this depleted or spent liquor isreheated and reused to dissolve more fresh bauxite.

Bauxite ores used in the Bayer process also contain silica in variousforms and amounts, depending on the source of the bauxite. The causticused to dissolve the aluminum minerals also dissolves part or all of thesilica content of the bauxite, especially the silica that is present inthe form of aluminosilicate clays. The silica rapidly dissolves in thedigestion step to form solutions that are supersaturated with respect tosilica. This dissolved silicate reacts relatively slowly with the sodiumaluminate in solution to form complex hydrated sodium aluminumsilicates, generally designated “desilication products.” The principaldesilication product is the species known as sodalite:3(Na₂O.Al₂O₃.2SiO₂.2H₂O)Na₂X, where X can be CO₃ ²⁻, 2Cl⁻, SO₄ ⁻², or2AlO₂ ⁻. Other related species such as cancrinite and noselite are alsopossible, so the more general term sodium aluminosilicate is preferred.All of these desilication products are of low solubility in the sodiumaluminate liquor and largely precipitate out of solution, therebyremoving undesirable silica from the solution.

The rate at which the desilication products precipitate out, however, isslow and even when a lengthy “predesilication” step is used,concentrations of dissolved silica remain well above equilibrium values.Some of this silica subsequently precipitates with the precipitatedalumina and contaminates the alumina. Even after the aluminaprecipitation step, silica concentrations are still above equilibriumvalues in the so-called “spent liquor”, and because of the reducedaluminum concentrations, the silica becomes easier to precipitate out,in the form of sodalite and related minerals. An essential part of theBayer process is to reheat this spent liquor so that it can be used todigest more bauxite ore. In the heat exchangers used to reheat theliquor, the higher temperatures increase the rate of aluminosilicateprecipitation and as a result, aluminosilicate deposits as “scale” onthe inside walls of the heat exchangers. The scale has low thermalconductivity compared to the steel of the walls and heat transfer isseverely reduced as scale builds up. This reduced heat transfer causedby aluminosilicate scaling is sufficiently severe that the heat exchangeunits have to be taken out of service and cleaned frequently, as oftenas every one to two weeks.

Scaling that is related to silica can be minimized to some extent by acombination of blending bauxite ores with different silica contents, byoptimizing the time and temperature of the digestion step, and by use ofa separate desilication step. The situation is however complicated bythe fact that silica in the solution or liquor is not necessarilyproportional to the silica in the starting bauxite. Since the Bayerprocess is continuous, or cyclical, silica would continually increase ifit were not removed from the system as aluminosilicate. Some silica isnecessary to increase supersaturation to initiate precipitation ofdesilication products. Bayer liquors are always supersaturated withrespect to silica and this excess silica can readily precipitate asaluminosilicate, especially onto the inside surfaces of heat exchangers.

There is considerable economic impact of aluminosilicate scale onalumina production. Cleaning of the heat exchangers with acid is itselfa high maintenance cost. The acid cleaning also reduces the life of theheat exchangers, therefore adding cost due to frequent replacement ofthe heat exchangers. Moreover, the reduced heat exchanger efficiencycaused by scaling leads to higher demand and cost for energy in the formof steam. The scaled pipes also result in decreased flow of liquor andpotentially lost production. Altogether the costs directly due toscaling constitute a significant portion of the cost of producingalumina.

Scale build up has also been known to be a problem in boiler watersystems and a number of treatments for reducing scale in boiler watersystems have been proposed. In boiler water systems, pH is generallyonly 8 to 9 and dissolved salts are usually not present inconcentrations more than about one to five grams/liter. Exemplarytreatments for scale in boilers include siliconate polymers such as thecopolymers of acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid(AMPS), and 3-(trimethoxysilyl)propyl-methacrylate as disclosed byMohnot (Journal of PPG Technology, 1 (1), (1995) 19-26). These polymerswere reported to reduce the amount of silica gel adhering to the wall ofpolytetrafluoroethylene bottles in tests done with 645 ppm SiO₂ at pH8.3 and 100° C., i.e., conditions approximating those in a boiler. AJapanese patent application (Kurita Water Ind. Ltd., 11-090488 (1999))also deals with adhesion of silica-type scale in cooling water or boilerwater systems. The compositions disclosed are vinyl silanol/vinylalcohol copolymers, which may also contain, e.g., allyl alcohol orstyrene. Tests were done in water that contained 200 mg/l silica at pH9.0 and temperatures of 45-75° C. Use of the subject compoundsreportedly led to less silica scale compared to an acrylic acid-AMPScopolymer.

In boilers the pH is generally quite mild, only 8 to 9 and dissolvedsalts are usually not present in concentrations more than about one tofive grams/liter. Additionally, scales formed in boiler water systemsconsist of primarily amorphous silica, although other scales such ascalcium carbonate, calcium phosphate, etc., are possible. In contrast,the supersaturated solutions at high temperatures and high pH ofessentially 14, make scaling problems much more serious and difficult tocontend with in plants that carry out the Bayer process than in boilers.In addition, the concentrations of dissolved salts (i.e., sodiumaluminate, sodium carbonate, sodium hydroxide, etc.) in the Bayerprocess are very high, such that total dissolved salt concentrations aregreater than 200 grams/liter. It is not surprising, therefore, that thescales that form in the Bayer process are distinctly different fromthose that form in boilers and unlike boiler scales, all Bayer scalescontain aluminum, which is expected because of the high concentrationsof aluminum in the Bayer solutions or liquors. In particular, thealuminosilicate scales contain equal numbers of aluminum and siliconatoms.

Thus, although there have been treatments available for boiler scales,there has been limited success in obtaining methods and/or chemicaladditives that reduce or eliminate aluminosilicate scaling in the Bayerprocessing of alumina. The earliest attempts appear to be the use of asiloxane polymer (a silicon-oxygen polymer with ethyl and —ONa groupsattached to the silicons), i.e.,

that reportedly reduced scaling during the heating of aluminatesolutions (V. G. Kazakov, N. G. Potapov, and A. E. Bobrov, TsvetnyeMetally (1979) 43-44; V. G. Kazakov, N. G. Potapov, and A. E. Bobrov,Tsvetnye Metally (1979) 45-48). It was reported that at the relativelyhigh concentrations of 50-100 mg/l, this polymer was effective inpreventing decrease of the heat transfer coefficient of heat exchangerwalls. Methods of altering the morphology of aluminosilicate scales havebeen disclosed using either amines and related materials (U.S. Pat. No.5,314,626 (1994)) or polyamines or acrylate-amide polymers (U.S. Pat.No. 5,415,782 (1995)). While these materials were shown to modify themorphology of the aluminosilicate particles, there were no examples ofreduction in the amount of scaling. Additionally, treatmentconcentrations required were quite high, in the range of 50 to 10,000parts per million.

Hence, thus far no economically practical materials or process has beenoffered to solve the problem of aluminosilicate scaling in the Bayerprocess industry. There is, in fact, currently no way at all toeliminate aluminosilicate scaling in the Bayer process. Because of thesevere problems caused by aluminosilicate scaling, it would be a greatbenefit to the industry to have a cost-effective treatment method thatwould reduce these problems and expenses.

SUMMARY OF THE INVENTION

The present invention solves the aforementioned problems and others byproviding materials and a process whereby polymers with the pendantgroup or end group containing —Si(OR)₃ (where R is H, an alkyl group,Na, K, or NH₄) are used to reduce or eliminate aluminosilicate scalingin a Bayer process. When materials of the present invention are added tothe Bayer liquor before the heat exchangers, they reduce and evencompletely prevent formation of aluminosilicate scale on heat exchangerwalls. Moreover, the present materials are effective at treatmentconcentrations that make them economically practical.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a process and materials for thereduction of aluminosilicate containing scale in the Bayer process. Theprocess comprises the step of adding to a Bayer process stream analuminosilicate containing scale inhibiting amount of a polymer havingpendant thereto a group or end group containing —Si(OR″)₃ where R″═H,C1-C3 alkyl, aryl, Na, K or NH₄. The present inventors have found thatthe scale reducing or inhibiting properties of the polymer having apendant group containing —Si(OR″)₃ where R″═H, C1-C3 alkyl, aryl, Na, Kor NH₄, attached thereto is not dependant on the configuration and/orsize of the polymer to which the group is attached. Therefore, anypolymer, having the requisite group containing —Si (OR″)₃ where R″═H,C1-C3 alkyl, aryl, Na, K or NH₄ attached thereto should therefore besuitable for use in the present invention.

In a preferred embodiment, the group containing —Si(OR″)₃, where R″═H,C1-C3 alkyl, aryl, Na, K or NH₄ comprises a group according to-G—R—X—R′—Si(OR″)₃ where G=no group, NH, NR″ or O; R=no group, C═O, O,C1-C10 alkyl, or aryl; X=no group, NR, O, NH, amide, urethane, or urea;R′=no group, O, C1-C10 alkyl, or aryl; and R″═H, C1-C3 alkyl, aryl, Na,K or NH₄. In one embodiment, the group is —NH—R—X—R′—Si(OR″)₃, whereR=no group, O, C1-C10 alkyl, or aryl; X═O, NH, an amide, urethane, orurea; R′=no group, O, C1-C10 alkyl, or aryl; and R″═H, C1-C3 alkyl,aryl, Na, K or NH₄. In another embodiment the polymer includes, but isnot limited to, a polymer according to the formula:

where x=0.1-100%, y=99.9-0%; and Q=H, C1-C10 alkyl, or aryl, COXR whereR═H, C1-C10 alkyl, aryl, X═O or NH; and (Q can be of more than onetype); and R″═H, C1-C10 alkyl, aryl, Na, K or NH₄. In another preferredembodiment a polymer according to the formula:

where w=1-99.9%, x=0.1-50%, y=0-50%, z=0-50%; andQ=C1-C10 alkyl, aryl, amide, acrylate, ether, COXR where X═O or NH andR═H, Na, K, NH₄, C1-C10 alkyl or aryl, or any other substituent; X═NH,NR″ or O; R′═C1-10 alkyl, or aryl; R″═H, C1-C3 alkyl, aryl, Na, K orNH₄; andD=NR′₂ or OR″, with the proviso that all R and R″ groups do not have tobe the same is used, wherein a polymer according to the formula:

where w=1-99.9%, x=0.1-50%, y=0-50%, z=0-50%; andQ is phenyl is a specific example.

In another preferred embodiment a polymer according to the formula:

where x=1-99%, y=1-99%, z=0.5-20% and M=Na, K, NH₄; andR″═H, C1-10 alkyl, aryl, Na, K or NH₄ is used; wherein a polymeraccording to formula:

where x=1-99%, y=1-99%, z=0.5-20% is a specific example.

The polymer to which the group is pendant can comprise at least onenitrogen to which the pendant group is attached. Exemplary polymerscomprising at least one nitrogen to which the pendant group is attachedinclude, but are not limited to, a polymer according to the followingformula:

where x=0.1-100%, y=99.9-0%; and R=no group, C1-C10 alkyl, aryl, or—COX—R′—, where X═O or NH and R′=no group, C1-C10 alkyl or aryl; andR″═H, C1-C3 alkyl, aryl, Na, K or NH₄; wherein a polymer according tothe formula:

where x=0.5-20%, y=99.5-80% and a polymer according to the formula:

where x=0.5-20%, y=99.5-80% are preferred.

In another embodiment the polymer having a —Si(OR″)₃ containing pendantgroup attached thereto is grafted to another polymer. Exemplary suchpolymers include, but are not limited to, polymers of the formulae:

where x=0.1-99% (as percentage of monomer units in the polymer) andX═NH, NR′ or O; R′═C1-C10 alkyl, or aryl and R″═H, C1-C3 alkyl, aryl,Na, K or NH₄, wherein

is a specific example.

The polymers used in the invention can be made in a variety of ways. Forexample, they can be made by polymerizing a monomer containing the group—Si(OR″)₃, where R″═H, C1-C3 alkyl, aryl, Na, K or NH₄, such as forexample a silane monomer, or copolymerizing such a monomer with one ormore co-monomers. Suitable silane monomers for use in the presentinvention include, but are not limited to vinyltriethoxysilane,vinyltrimethoxysilane, allyltriethoxysilane, butenyltriethoxysilane,gama-N-acrylamidopropyltriethoxysilane, p-triethoxysilylstyrene,2-(methyltrimethoxysilyl)acrylic acid, 2-(methyltrimethoxysilyl)-1,4butadiene, N-triethoxysilylpropyl-maleimide and other reaction productsof maleic anhydride and other unsaturated anhydrides with aminocompounds containing the —Si(OR″)₃ group. These monomers can behydrolyzed by aqueous base, either before or after polymerization.Suitable co-monomers for use in the present invention include, but arenot limited to, vinyl acetate, acrylonitrile, styrene, acrylic acid andits esters, acrylamide and substituted acrylamides such asacrylamidomethylpropanesulfonic acid. The copolymers can also be graftcopolymers such as polyacrylic acid-g-poly(vinyltriethoxysilane) andpoly(vinyl acetate-co-crotonic acid)-g-poly(vinyltriethoxysilane). Thesepolymers can be made in a variety of solvents. Solvents suitable forsuch use include, but are not limited to, acetone, tetrahydrofuran,toluene, xylene, etc. In some cases the polymer is soluble in thereaction solvent and is recovered by stripping off the solvent.Alternatively, if the polymer is not soluble in the reaction solvent,the product is recovered by filtration. Suitable initiators for use inthe present invention include, but are not limited to,2,2′azobis(2,4-dimethylvaleronitrile) and 2,2-azobisisobutyronitrile,benzoyl peroxide, and cumene hydroperoxide.

In another embodiment of the present invention, polymers useful in theinvention can be made by reacting a compound containing a —Si(OR″)₃group as well as a reactive group that reacts with either a pendantgroup or backbone atom of an existing polymer. For example, polyaminescan be reacted with a variety of compounds containing —Si(OR″)₃ groupsto give polymers which can be used for the invention. Suitable reactivegroups include, but are not limited to an alkyl halide group, such asfor example, chloropropyl, bromoethyl, chloromethyl, and bromoundecyl.The compound containing —Si(OR″)₃, can contain an epoxy functionalitysuch as glycidoxypropyl, 1,2-epoxyamyl, 1,2-epoxydecyl or3,4-epoxycyclohexylethyl. The reactive group can also be a combinationof a hydroxyl group and a halide, such as 3-chloro-2-hydroxypropyl. Thereactive moiety can also contain an isocyanate group, such asisocyanatopropyl, or isocyanatomethyl that react to form a urea linkage.In addition, silanes containing anhydride groups, such astriethoxysilylpropylsuccinic anhydride are suitable for use in makingthe polymers for the present invention. The reactions can be carried outeither neat or in a suitable solvent. In addition, other functionalgroups such as alkyl groups can be added by reacting other amino groupsor nitrogen atoms on the polymer with alkyl halides, epoxides orisocyanates. The polyamines can be made by a variety of methods. Theycan be made by a ring opening polymerization of aziridine or similarcompounds. They also can be made by condensation reactions of aminessuch as ammonia, methylamine, dimethylamine, ethylenediamine etc. withreactive compounds such as 1,2-dichloroethane, epichlorohydrin,epibromohydrin and similar compounds.

Polymers containing anhydride groups can be reacted with a variety ofcompounds containing —Si(OR″)₃ to make polymers suitable for use in thepresent invention. Suitable anhydride containing polymers include, butare not limited to, maleic anhydride homopolymer, and copolymers ofmaleic anhydride with monomers such as styrene, ethylene andmethylvinylether. The polymer can also be a graft copolymer such aspoly(1,4-butadiene)-g-maleic anhydride or polyethylene-g-maleicanhydride and the like. Other suitable anhydride monomers include, butare not limited to, itaconic and citraconic anhydrides. Suitablereactive silane compounds include, but are not limited toγ-aminopropyltriethoxysilane, bis(gama-triethoxysilylpropyl)amine,N-phenyl-gama aminopropyltriethoxysilane, p-aminophenyltriethoxysilane,3-(m-aminophenoxypropyl)-trimethoxysilane, andgama-aminobutyltriethoxylsilane. Other functional groups can be added tothe polymer by reacting it with amines, alcohols and other compounds. Ina preferred polymer for use in the present invention, maleic anhydrideis the anhydride and the co-monomer is styrene. A preferred silane isgama-aminopropyltriethoxysilane. It is also advantageous to react someof the anhydride groups with another amine such as diethylamine.

The same type of amino compound containing an —Si(OR″)₃ group can bereacted with polymers containing a pendant isocyanate group, such ascopolymers of for example, isopropenyldimethylbenzylisocyanate and vinylisocyanate, with co-monomers including, but not limited to, vinylacetate, styrene, acrylic acid, and acrylamide. These polymers can alsobe reacted with other compounds such as amines to enhance performance.

Isocyanate functional compounds with an —Si(OR″)₃ group such asgama-isocyanatopropyltrimethoxysilane can also be reacted with polymerscontaining hydroxyl groups such as hydrolyzed poly(vinyl acetate) andcopolymers of vinyl acetate with other monomers. Other hydroxylcontaining polymers suitable for use include, but are not limited to,polysaccharides and polymers containing N-methylolacrylamide.

In the present process, the amount of polymer added to the processstream can depend on the composition of the Bayer liquor involved andgenerally all that is required is an aluminosilicate containing scaleinhibiting amount thereof. In general the polymer is preferably added tothe process stream in economically and practically favorableconcentrations. A preferred concentration is one that is greater thanabout 0 ppm to about 300 ppm, more preferably in a concentration that isgreater than about 0 ppm to about 50 ppm and most preferably the polymeris added to the process stream in a concentration that is greater thanabout 0 ppm to about 10 ppm.

The polymer can be added directly to the apparatus in which theformation of aluminosilicate containing scale is to be inhibited. It ispreferred, however to add the polymer to a charge stream or recyclestream or liquor leading to the particular apparatus. While the polymercan be added to the Bayer process stream at any time during the process,it is preferable to add it at any convenient point in the Bayer processbefore or during application of heat. Usually, the polymer is addedimmediately before the heat exchangers. The polymer could also be added,e.g., to the liquor before alumina precipitation or any other pointbetween the precipitators and the heat exchangers.

EXAMPLES Test procedure

A synthetic Bayer liquor is made by adding 12 ml of a sodium silicatesolution (27.7 g/l of a sodium silicate solution that is 28.9% SiO₂) to108 ml of a sodium aluminate solution that contains sodium aluminate,excess sodium hydroxide, and sodium carbonate. After mixing, thesolution contains 0.8 g/l SiO₂, 45 g/l Al₂O₃, 150 g/l NaOH, and 40 g/lNa₂CO₃. If a scale reducing additive is used, it is added just beforethe silicate is added to the aluminate solution (generally the additiveis used as a solution containing 1-10% of active reagent). This solutionis put into a polyethylene bottle along with a strip of pre-weighedclean mild steel (25 mm×95 mm) and the sealed bottle is heated withagitation at 100° C. for 18±2 hours. Eight to twelve such tests(bottles) are done at one time. At the end of the 18 hours, the bottlesare opened, the steel strip is thoroughly rinsed and dried, and thesolution is filtered (0.45μ filter). Considerable aluminosilicate scaleis observed to form on both the steel surface and as loosealuminosilicate in the liquor (which may have initially formed on thepolyethylene surfaces). The weight gain of the steel is a measure of theamount of aluminosilicate scaling (with no additive, the weight gain onthe steel is typically about 30 mg). In the examples below, the weightof scale formed on the steel strip is expressed as a percentage of theaverage weight of scale that formed on two blanks (i.e, no additiveused) that were part of the same set of tests. Similarly, the totalamount of aluminosilicate precipitated is also a measure of antiscalantactivity and this may be expressed as a percentage of the totalaluminosilicate that formed in the two blank experiments that were partof the same set of tests (with no additive, the total aluminosilicateprecipitated is typically about 150 mg).

Comparative Example A

A commercial sample of potassium methyl siliconate, similar to thepolymer described by Kazakov, et al., is diluted to 5% polymer in 2%NaOH. It is used in accordance with the Test Procedure described abovewith the following results reported in Table A.

TABLE A Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 300 97 84 1000 30 57 *no additiveIt was observed that operating at this very treatment concentration isnot practical for a commercial operation.

Example 1

A polymer with the structure

is made as follows: 42 g of a styrene-maleic anhydride (SMA) copolymer,with a mole ratio of styrene to maleic anhydride of 2.0, is dissolved in87 g of acetone. A separate solution is made with 3.03 g ofgama-aminopropyltriethoxysilane, 8.02 g of diethylamine and 21 g ofacetone. The amine solution is then added to the polymer solution andallowed to react for 15 minutes at ambient temperature. One hundredeighty milliliters (180 ml) of deionized (D.I.) water is mixed with 20ml of 28% aqueous ammonia and heated to 70° C. The aqueous ammonia isthen added to the polymer solution and the mixture heated to 65° C. toevaporate the acetone. The result is a solution containing 23.4% polymerbased on the total weight of SMA polymer and the two amines. It istested in accordance with the Test Procedure described above with thefollowing results reported in Table B.

TABLE B Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 300 0 0 50 0 0 10 0 0 *no additive

Example 2

A 25.0 g aliquot of the polymer solution from Example 1 is added to 200ml of isopropanol to precipitate the polymer, which is washed withisopropanol and dried. The dried polymer contains 0.80% silicon. A 2%solution of the isolated polymer is made in a mixture of NaOH andaqueous ammonia. It is tested in accordance with the Test Procedure withthe results reported in Table C.

TABLE C Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 300 0 0 50 0 0.2 10 0 0.1 *no additive

Comparative Example B

A polymer with the structure

is made by reacting the same SMA polymer used in Example 1 withdiethylamine in acetone and then adding warm aqueous ammonia to give anaqueous solution containing 23.4% polymer, which is diluted to 2%polymer with 2% aqueous NaOH. This is tested in accordance with the TestProcedure with the results reported in Table D.

TABLE D Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 300 137 103 50 183 97 10 125 97 *no additive

Example 3

An amine polymer with the structure

is made as follows: 2.3 g of gama-isocyanatopropyltriethoxysilane ismixed with 20 g of a polyethyleneimine. After 30 min. at ambienttemperature, 1.0 g of the mixture is diluted to 20.0 g with 2% NaOH.This polymer solution is tested in accordance with the Test Procedure aspreviously described. Results are reported in Table E.

TABLE E Scale on steel, % vs. Total sodalite formed, % Dose blank* vs.blank* 300 88 29 50 183 65 10 172 94 *no additive

Example 4

A polymer containing the pendant groups

is made from a commercial copolymer of maleic anhydride grafted ontopolybutadiene. (The anhydride equivalent weight is given as 490.)

Twenty grams (20 g) of the polymer is dissolved in 80 g of acetone. 0.90g of aminopropyltriethoxysilane is mixed with 10 g of acetone. The aminesolution is then added to the polymer solution and allowed to react for15 minutes at ambient temperature. 100 ml of D.I. water is mixed with 10ml of 28% aqueous ammonia and heated to 70° C. The aqueous ammonia isthen added to the polymer solution and the mixture heated to 65° C. toevaporate the acetone. The resulting aqueous solution contains 15.1%polymer. The solution is diluted to 5% polymer in 2% NaOH and tested inaccordance with the Test procedure with the following results reportedin Table F.

TABLE F Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 300 1.1 7.6 100 10.0 19.9 *no additive

Example 5

Eighteen (18.00) grams of polyethyleneimine is mixed with 2.00 grams ofchloropropyltrimethoxysilane and the mixture is heated at 100° C. for 16hours to give the product shown below.

A portion of the product is dissolved in water containing 20 g/l NaOHand this solution is used in accordance with the Test Proceduredescribed above and the results are reported in Table G.

TABLE G Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 200 0 0 100 0 0 50 4 1 *no additive

Example 6

5.56 g of 50% NaOH is added to a solution consisting of 16.00 gacrylamide and 41.2 g water. 4.00 g vinyltriethoxysilane is then added.0.2 g of azobis-isobutyronitrile in 6 ml ethanol is added and themixture is heated at 70° C. The resulting polymer is found to containsilicon as expected from the structure below, following hydrolysis inNaOH solution, which also converts a majority of the amide functionalityto carboxyl groups:

A solution of this polymer is tested in accordance with the TestProcedure and the results are reported in Table H.

TABLE H Dosage, Scale on steel, % vs. Total sodalite formed, % mg/lblank* vs. blank* 300 4 23 100 6 5 *no additive

Changes can be made in the composition, operation and arrangement of theprocess of the present invention described herein without departing fromthe concept and scope of the invention as defined in the followingclaims.

1. A polymer for use in the reduction of aluminosilicate containingscale according to the formula:

where: x=1-99%, y=1-99%, z=0.5-20% and M=Na, K, NH₄; and R″═H, C1-C3alkyl, aryl, Na, K or NH₄.
 2. The polymer in accordance with claim 1according to the formula:

where: x=1-99%, y=1-99%, z=0.5-20%.
 3. A polymer for use in thereduction of aluminosilicate containing scale, wherein the polymer is agraft copolymer of Formula a or Formula b:

where x=0.1-99% (as percentage of monomer units in the polymer) andX═NH, NR′ or O; R′═C1-C10 alkyl, or aryl and R″═H, C1-C3 alkyl, aryl,Na, K or NH₄.